Above-Inversion Profiles of Moisture and Ozone Observed during FIRE

Abstract

Data from the First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment (FIRE) were combined with NOAA synoptic products, a trajectory analysis scheme, and satellite imagery to document the existence and causes of layers of air characterized by high ozone concentrations and low specific-humidity values, as well as layers of air characterized by high specific-humidity values and low ozone concentrations above the summertime marine stratocumulus cloud deck off the coast of California. The ozone concentrations and specific-humidity values observed were larger than those expected in the region just above the subsidence inversion off the California coast. The layers with high ozone concentrations appear to be extruded from the middle or upper troposphere. The layers with high specific-humidity values result from frontal lifting associated with surface cyclones upstream of the marine stratocumulus regime. Both types of layers can become embedded in the flow around the Pacific subtropical anticyclone and can alter the thermodynamic structure above the marine stratocumulus cloud regime. The impact of these layers on the marine stratocumulus cloud regime is also analyzed using boundary-layer model simulations.